Impellers, especially single vane impellers for rotary pumps



March 26, 1963 w. B USCHHORN 3,

IMPELLERS, ESPECIALLY SINGLE VANE IMPELLERS FOR ROTARY PUMPS Filed June15, 1959,

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Unite 3,082,695 MELLERS, ESPEQIALLY SINGLE VANE IMPELLERS FOR ROTARYPUMPS Walther Buschhorn, Pegnitz, Upper Franconia, Germany, assignor toKlein, Sehanzlin & Becker Aktiengesellschaft, Frankenthal (Pfalz),Germany Filed June 15, 1959, Ser. No. 820,506 2 Claims. (Cl. 103115) Therunning of rotary pumps free from oscillations and vibrations isgoverned primarily by the construction of the impellers employed,whereby unequal distribution of the mass of the individual elements ofthe impeller in the course of their manufacture has a particularlydisturbing eflect. Consequently the impellers are dynamically balancedon a special machine before being fitted in the pump housing. It isknown that a dynamically well-balanced impeller, particularly one havingonly a single vane, is not capable of ensuring perfect running of therotary pump. This is due to the fact that the transmission of energy tothe liquid being pumped is not uniform along the impeller with theresult that the reaction forces resulting therefrom cause one-sidedpressure of the impeller against the stuffing-box bearing, packing gapsand the like, and premature wear at these points. This hydraulicunbalance of the rotary pumps is overcome in known manner by increasingthe number of vanes of the impeller. Rotary pumps for delivering liquidspermeated with long-fibrous and band-like impurities are preferablyequipped with single vane impellers so as to avoid the danger of chokingor clogging which has to be feared. It has hitherto been endeavoured toeliminate the hydraulic unbalance which is particularly apparent in theimpellers, by arranging a suitable counterweight on the back of theimpeller vane. This counterweight is naturally dependent upon the numberof revolutions and the size as well as the total weight of the impellerand also upon the specific gravity of the liquid to be dealt with. As itis theoretically not determinable, it has to be ascertained empiricallyfor each impeller. It has already been attempted to eliminate thehydraulic unbalance in the case of single vane impellers by twisting thevane in spiral shape. In this known type of impellers it is alsonecessary to determine the shape of the vane empirically for eachimpeller separately.

The object of the present invention is to produce an impeller which isnot open to the above-mentioned objections. This is attained by plottingthe curve of the vane so that the increase in work per vane element isthe same on opposite sides of the impeller. This measure becomesparticularly effective in the case of an impeller provided with only asingle vane extending approximately through 360, because the shape ofthe vane which is mostly very complicated and was hitherto ascertainedonly empirically, can be determined already in the course of designing.Moreover, it is likewise advantageous to plot the thickness course ofthe vane so that its center of mass coincides with the axis ofrotations. This renders unnecessary the simultaneous casting of suitablecounterweights on the back of the impeller in the manner alreadypracticed.

To ascertain the course of the vane of the impeller according to theinvention, use is made of the known Euler fundamental equation InEquation I H =the theoretical lift of the pump,

w=the angular speed of the impeller,

g=the acceleration due to gravity,

r =the radius distance of the vane at the outlet in relation to the axisof rotation of the vane,

As a guiding device is not usually arranged in front of the impeller,the last term in the bracket of the Equatlolll I: r -c will be equal tozero, so that the general formu a is obtained. Herein r=the radiusdistance of a vane element, in relation to the axis of rotation of theimpeller,

c =the tangential component of the absolute speed c at the point of thevane element having the radius distance r.

The work of the impeller according to the invention transmitted by thevane to the liquid being pumped can be expressed by the equation:

wherein k=a constant and go=llhe angle at the center, measured betweenthe beginning of the vane and the vane element with the radius r.

The constant k is obtained by dividing the given total blade work H andthe angle at the centre o between which the vane should or is to extend.

Thus with the Equation III it is found that the vane work H increases inproportion with the angle at the center. Thereby the condition is met atthe same time that the same amount of work is transmitted to the liquidbeing pumped by vane elements opposite to each other.

If the Equation II is treated in the same way as Equation 111 andreduced according to the (p into the form the course of the vane isclearly determined.

The tangential component c is, according to FIGURE 1, dependent bothupon the radius r and also upon the angle at the center to in the form:

are inserted, when in Equation Vb V=volume of the quantity delivered,b=the width of the vane, and the value for 0,, is inserted in IV, theresult will be Equation VI represents a linear difierential equation of1st order. Its solution reads 3 The integration constant C is for =Cg1:2, is equal to g-21r-l7)-k+ C w-21r-b 71 w V g-21r-b-k+ If this valuefor C is inserted in Equation VII the final solution of the differentialEquation VII reads:

vr-w 'l) 7'1 In FIGURES 1 to 3 of the drawing the subject matter of theinvention and the above deductions are explained in detail. FIGURE 1 isa diagram of the values used for the deduction for determining thecurvature of the vane. This figure shows in particular the relationshiprepresented by the Equation V.

FIGURE 3 shows the result of an example calculated with the aid of theabove developed relationships for a single vane impeller. Here the anglep dependent upon the radial distance of the vane elements is tracedgraphically. The example is based on a delivery quantity of V=446.4cubic metres per hour, a speed of 1 100 rpm, a constant impeller widthof b=130= nuns. and a distance 3 at the beginning of the blade equal to110 mms. The shape of the vane is shown in FIGURE 4 as calculated fromthe values of FIGURE 3.

I claim:

1. An impeller for centrifugal pumps, substantially providing hydraulicequalization over the entire operating range, comprising an impeller,the passage of which is formed by a single vane extending in the form ofa spiral approximately over 360, the curve of said spiral essentiallyconforming to the equation =the angle at the center, measured betweenthe beginning of the vane and the vane element with the radius r,

r=the radius distance of a vane element in relation to the axis ofrotation of the impeller,

r =the radius distance of the vane at the inlet in rela tion to the axisof rotation of the vane,

V=the volume of the quantity delivered,

g: the acceleration due to gravity,

b the width of the vane,

w=the angular speed of the impeller,

k=a constant equal to the quotient of the requested theoretical pressurehead H and the angle at the center (p so that the work increase per vaneelement is the same on opposite sides of the impeller.

2. An impeller for centrifugal pumps substantially providing hydraulicequalization over the entire operating range, comprising an impeller,said impeller being formed by a single vane which extends in the form ofa spiral over essentially 360 and defines a pumping passage extendingfrom a point adjacent the axis of the impeller to the periphery thereof,said blade defining consecutive blade elements each having a radialdistance r with respect to the axis of rotation of the blade assigned toa center angle measured from the leading edge of the blade to therespective blade element, the volume of said passage determined by saidcenter angle being equal to the quotient of the product of apredetermined angular velocity of the impeller, said radial distance rof the respective blade element, and the tangential component c of theflow of circulation on this element and the product of the accelerationdue to gravity and a constant k, which constant is equal to the quotientof a predetermined theoretical pressure head H and said center angleover which the blade is to extend so that the work increase per bladeelement is the same on opposite sides of the impeller in any radialplane.

References Cited in the file of this patent UNITED STATES PATENTS450,491 Nicholas et al Apr. 14, 1891 963,378 Lorenz July 5, 19102,245,035 Hartman June 10, 1941 2,655,868 Lindau et al Oct. 20, 19532,853,019 Thornton Sept. 23, 1958 FOREIGN PATENTS 1,324 Great Britain of1863 23,234 Germany Dec. 30, 1881 340,152 Great Britain Dec. 24, 1930

1. AN IMPELLER FOR CENTRIFUGAL PUMPS, SUBSTANTIALLY PROVIDING HYDRAULIC EQUALIZATION OVER THE ENTIRE OPERATING RANGE, COMPRISING AN IMPELLER, THE PASSAGE OF WHICH IS FORMED BY A SINGLE VANE EXTENDING IN THE FORM OF A SPIRAL APPROXIMATELY OVER 360*, THE CURVE OF SAID SPIRAL ESSENTIALLY CONFORMING TO THE EQUATION 